Iraqi men fill military trucks to join the Iraqi army June 14 at the main recruiting center in Baghdad, Iraq after authorities urged Iraqis to help battle insurgents. (Karim Kadim / AP)

This image posted on a militant website June 14 appears to show militants from the al-Qaida-inspired Islamic State of Iraq and the Levant (ISIL) with captured Iraqi soldiers wearing plain clothes after taking over a base in Tikrit, Iraq. (AP)

BAGHDAD — The United States said Sunday it was evacuating some staff from its embassy and beefing up security as deadly explosions rocked the Iraqi capital and advancing militant Islamic insurgents released graphic images appearing to show its fighters massacring captured Iraqi soldiers.

The U.S. State Department said in a statement that an undisclosed number of staffers will be moved to Amman, Jordan or U.S. consulates elsewhere in Iraq not immediately threatened by the insurgent group, the Islamic State of Iraq and the Levant, or ISIL.

It said the embassy would remain fully operational with “some additional U.S. government security personnel.” The embassy, inside the Green Zone near the Tigris River, employs thousands of people, some local hires and others from the United States.

The development came as photos posted on a militant website show what look to be masked fighters of the Islamic State of Iraq and the Levant loading captives onto flatbed trucks before forcing them to lie face-down in a shallow ditch with their arms tied behind their backs. The bodies of the captives are then shown, soaked in blood after being shot.

The Associated Press said the images were verified and were consistent with its reporting. Iraq’s top military spokesman, Lt. Gen. Qassim al-Moussawi, confirmed the authenticity of the photos Sunday and said he was aware of cases of mass murder of Iraqi soldiers.

Meanwhile, a string of explosions in Baghdad killed at least 15 and wounded more than 30 on Sunday. A car bomb early Sunday killed 10 and wounded 21 in the city center. After nightfall, another explosion went off in the area, killing two and wounding five. A third blast hit near a falafel shop in the Sadr City district, killing three and wounding seven.

Still, the Iraqi military pointed to signs of progress its troops were regaining their footing.

The Iraqi military repelled an assault by insurgents on a strategic town close to the Syrian border, military officials said. Fierce fighting erupted in the early morning hours in Tal Afer, about 30 miles west of Mosul, and the only larger town in Nineveh province not under control by ISIL.

“The army with the help of residents of the city managed to stop the attack on the city,” said Qassim Atta, spokesman for the Iraqi military.

Military officials said army helicopters destroyed 50 cars full of ISIL fighters Sunday, adding it also killed 279 “terrorists” in the past 24 hours.

Residents who fought against the militants described a chaotic scene.

“The ISIL attacked the town from four directions but we were ready to fight back,” said Mohamad Ahmad, a resident of Tal Afer. “We endured for hours, they came in big numbers and we fought along with Iraqi army to protect the city.”

Tal Afer is strategic city and ISIL considers it key to their plan to create an Islamic state spanning Iraq and Syria.

After stunning gains last week including two provincial capitals, Mosul and Tikrit, the advance toward Baghdad was slowed about 30 miles away from the capital with Iraqi commanders saying their forces were now starting to push the militants back, and that soldiers had recaptured two towns north of Baghdad.

The crisis prompted Secretary of Defense Chuck Hagel on Saturday to order the aircraft carrier USS George H. W. Bush and two other shops into the Persian Gulf as the U.S. weighs options for responding to the situation as some Congressmen call for airstrikes.

Rep. Mike Rogers, R-Mich., chairman of the House intelligence committee and Sen. Lindsey Graham, R-S.C., argued Sunday on Fox News and CBS, respectively, that the insurgents’ success will create a safe haven for planning terrorist activity against the U.S.

While talking on CNN’s “State of the Union,” Graham said the U.S. should engage in talks with Iran to negotiate a settlement in Iraq.

“The Iranians can provide some assets to make sure Baghdad doesn’t fall. We need to coordinate with the Iranians,” he said.

In Tikrit, Iraqi troops made their way to a military camp north of the city in an attempt to regroup and retake it. A senior Iraqi officer said they have stopped the movement of militants in the city and are awaiting orders to retake all of Tikrit. He spoke on the condition of anonymity because he was not authorized to speak to the press.

In Mosul, life started returning to normal, residents reported as ISIL removed checkpoints and reopened roads. But residents worried over instructions from militants dictating behavior, saying the directives encroached on their personal freedoms.

“These oblige women to wear loose clothing and only to leave home when absolutely necessary,” said Busra Mohammed, 34, a teacher there. “We reject such instructions that want to take us back hundreds of years because they are incompatible with the rights of women and an insult to their dignity.”